早苗 伊藤

Multi-scale transport simulation with ion temperature gradient driven drift wave turbulence

The gyro-fluid model proposed by Ottaviani et al. is extended, in which the ion parallel flow and ion neoclassical viscosity are taken into account. The heat source is also introduced. Using this model, the ion temperature gradient driven drift wave turbulence is analyzed. The reversed shear profile is employed, and internal transport barrier formation and collapse is investigated during the heating process. The multi-scale interaction between the thermal transport and the ITG turbulence is observed. In the saturation phase, the system approaches to marginal state, where the energy supply from source and intermittent transport with the avalanche process are balanced.

Nonlinear Simulation of Ion Temperature Gradient Driven Drift Wave Turbulence

The gyro-fluid model proposed by Ottaviani et. al is extended, in which the ion parallel flow and ion neoclassical viscosity are taken into account. Using this model, the ion temperature gradient driven drift wave turbulence is analyzed. The saturation level and ion heat flux are evaluated in case with profile relaxation. The multi-scale interaction between the micro-scale and meso-scale is observed in our simulations. The avalanche process and turbulence spreading occur in the nonlinear phase. In addition, the various kind of parallel scheme are tested to improve the performance of the code. We find a way which gives better parallel efficiency of the spectral code.

Numerical Analysis of Ion Temperature Gradient Driven Drift Wave

We have developed global ITG (Ion Temperature Gradient Driven Drift Wave) turbulence code to investigate anomalous ion transport in tokamak plasmas. The gyro-fluid model is extended to incorporate accurate form of neoclassical viscosity. Firstly, we have performed the linear analysis of ITG mode using this code. The dependence of growth rate on various parameters are examined. Next, we have done nonlinear simulations to investigate neoclassical effect on zonal flow damping and saturation amplitude of ITG turbulence. The weak dependence of saturation level on neoclassical viscosity is found in our simulations.